Stent with Tether Interfaces

ABSTRACT

A radially-expandable stent is shaped so as to define a plurality of tether interfaces, a plurality of lower-securement portions, and a plurality of higher-securement portions. The lower-securement portions extend (a) along at least respective contiguous lower-securement axial segments of the stent and (b) circumferentially around respective contiguous lower-securement circumferential portions of the stent, which lower-securement axial segments and lower-securement circumferential portions include one or more of the tether interfaces. The higher-securement portions extend (a) along at least respective contiguous higher-securement axial segments of the stent and (b) circumferentially around respective higher-securement circumferential portions of the stent, collectively at all circumferential locations other than those of the lower-securement circumferential portions. The lower- and the higher-securement portions alternate around the stent. The stent is shaped so as to define a plurality of outward protrusions at respective circumferential locations around the higher-securement portions, and not around the lower-securement portions.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a divisional of U.S. application Ser. No.14/773,640, filed Sep. 8, 2015, which is the U.S. national stage ofInternational Application PCT/IL2014/050233, filed Mar. 9, 2014, whichclaims priority from US Provisional Application 61/783,224, filed Mar.14, 2013, which is assigned to the assignee of the present applicationand is incorporated herein by reference.

FIELD OF THE APPLICATION

The present invention relates generally to stents, and specifically tostents for anchoring within body lumens.

BACKGROUND OF THE APPLICATION

Stents are used for various cardiovascular applications, such as to keepcoronary vessels open, to act as grafts in abdominal aortic aneurisms(“AAAs”), to anchor vena cava filters, or to act as a frame for aorticvalves. Stents are generally cylindrical, conical, or bottle shaped, andare designed to exert a radial force towards the vessel in which theyare implanted. The resulting friction force provides securement of thestent to the vessel, thereby preventing migration of the stent afterimplantation. Techniques for increasing stent securement includeproviding hooks or barbs, shaping the stent into a truncated cone, andprotruding the stent struts.

Functional tricuspid regurgitation (FTR) is governed by severalpathophysiologic abnormalities such as tricuspid valve annulardilatation, annular shape, pulmonary hypertension, left or rightventricle dysfunction, right ventricle geometry, and leaflet tethering.Treatment options for FTR are primarily surgical. The current prevalenceof moderate-to-severe tricuspid regurgitation is estimated to be 1.6million in the United States. Of these, only 8,000 patients undergotricuspid valve surgeries annually, most of them in conjunction withleft heart valve surgeries.

SUMMARY OF THE APPLICATION

Some applications of the present invention provide an anchoring system,which comprises a radially-expandable stent, and typically one or moretissue anchors and one or more tethers that connect the stent to the oneor more tissue anchors. The stent is configured to be implanted in abody lumen, such as a blood vessel. The stent typically lacks rotationalsymmetry, because some of the struts of a circumferential portion of thestent protrude outwardly and thereby define a polygonal shape, while thestruts of another contiguous circumferential portion of the stent do notprotrude outwardly and thereby define a cylindrical shape.

The circumferential portion with the outward protrusions exhibits highersecurement forces with the wall of the body lumen than does thecircumferential portion without the outward protrusions, thus allowingrelative axial movement of the non-protruding circumferential portionwhile maintaining the stent as a whole secured in the body lumen. Suchselective securement may relieve stresses in the stent frame resultingfrom cyclic loads applied to the stent (e.g., cyclic cardiac loads) atthe one or more tether circumferential locations, thereby enablinghigher fatigue endurance in the stent.

For some applications, when unconstrained in a radially-expanded state,the stent is generally tubular and shaped so as to define:

-   -   one or more tether interfaces at one or more tether        circumferential locations, respectively, each of which tether        interfaces extends circumferentially contiguously around less        than 30 degrees of a circumference of the stent;    -   a lower-securement portion that extends (a) along at least a        contiguous lower-securement axial segment of the stent and (b)        circumferentially around a contiguous lower-securement        circumferential portion of the stent, which lower-securement        axial segment and lower-securement circumferential portion        include the one or more tether interfaces;    -   a higher-securement portion that extends (a) along at least a        contiguous higher-securement axial segment and (b)        circumferentially around a higher-securement circumferential        portion of the stent at all circumferential locations other than        those of lower-securement circumferential portion. The        higher-securement circumferential portion typically extends        around between 215 and 330 degrees of the circumference of the        stent (e.g., at least 270 degrees of the circumference); and    -   a plurality of outward protrusions at respective outward        circumferential locations around the higher-securement portion,        and not around the lower-securement portion.

The outward protrusions of the higher-securement portion cause thehigher-securement portion to apply greater securement forces against thebody lumen wall than applied by the lower-securement portion, whichlacks outward protrusions. Such selective securement allows relativeaxial reciprocating movement of struts of the lower-securement portion,while maintaining the stent as a whole secured in the body lumen. Asdescribed above, such selective securement may thus relieve stresses inthe stent frame resulting from cyclic loads applied to the stent (e.g.,cyclic cardiac loads) at the one or more tether circumferentiallocations, thereby enabling higher fatigue endurance in the stent, andreducing the risk of stent migration.

For some applications, the outward protrusions arerotationally-asymmetrically distributed around the circumference of thestent, when the stent is unconstrained in the radially-expanded state.Alternatively or additionally, for some applications, the outwardprotrusions are periodically distributed around the higher-securementcircumferential portion, when the stent is unconstrained in theradially-expanded state. Typically, the outward protrusions are blunt,when the stent is unconstrained in the radially-expanded state. Thus,the securement is achieved using the stent struts themselves, withoutthe need for additional features such as barbs or hooks which increasethe crimp size of the stent without adding to radial stiffness.Additionally, because the outward protrusions are blunt, the implant maybe less likely to cause body lumen dissection than if sharp anchoringelements were provided.

For some applications, struts of the stent are shaped so as to define aplurality of columnar struts and a plurality of circumferential stentmeanders, coupled to the columnar struts at respective axial locations.Typically, each of the circumferential stent meanders is disposed aroundthe entire circumference of the stent. A set of one or more of thecircumferential stent meanders are shaped so as to define the outwardprotrusions at the respective outward circumferential locations aroundthe higher-securement portion, when the stent is unconstrained in theradially-expanded state.

For some applications, when the stent is unconstrained in theradially-expanded state, at least one of the circumferential stentmeanders is shaped so as to define (a) around the higher-securementportion, the outward protrusions (the circumferential stent meander maythus define a polygon if projected onto a plane perpendicular to alongitudinal axis of the stent), and (b) around the lower-securementportion, an arc of a circle if the circumferential stent meander isprojected onto the plane perpendicular to the longitudinal axis of thestent. For some applications, exactly one, exactly two, exactly three,exactly four, or five or more of the circumferential stent meanders arethus shaped.

In contrast, the other circumferential stent meanders do not define theoutward protrusions, and thus define respective circles if projectedonto the plane perpendicular to the longitudinal axis of the stent. Thestent may be shaped to define other polygon-circular shape patterns(e.g., every x circumferential stent meanders may define outwardprotrusions, such as every second meander, or every third meander). Forsome applications, the lower-securement portion is generally shaped as acircumferential portion of a circular cylinder.

For some applications, the stent is shaped so as to define one or more(e.g., exactly one) tension-distributing elements, which (a) extendalong at least a tether-distribution axial segment of the stent at theone or more tether circumferential locations, respectively, (b) definethe one or more tether interfaces, respectively, and (c) are configuredto distribute tension applied by the one or more tethers, respectively,along the tether-distribution axial segment.

There is therefore provided, in accordance with an application of thepresent invention, apparatus including:

a radially-expandable stent, which, when unconstrained in aradially-expanded state, is generally tubular and shaped so as todefine:

-   -   one or more tether interfaces at one or more tether        circumferential locations, respectively, each of which tether        interfaces extends circumferentially contiguously around less        than 30 degrees of a circumference of the stent,    -   a lower-securement portion that extends (a) along at least a        contiguous lower-securement axial segment of the stent and (b)        circumferentially around a contiguous lower-securement        circumferential portion of the stent, which lower-securement        axial segment and lower-securement circumferential portion        include the one or more tether interfaces,    -   a higher-securement portion that extends (a) along at least a        contiguous higher-securement axial segment of the stent and (b)        circumferentially around between 215 and 330 degrees of the        circumference, at all circumferential locations other than those        of the lower-securement circumferential portion, and    -   a plurality of outward protrusions at respective circumferential        locations around the higher-securement portion, and not around        the lower-securement portion;

one or more tissue anchors; and

one or more tethers having respective first longitudinal portions thatare coupled to the one or more tether interfaces, respectively, andrespective second longitudinal portions, different from the respectivefirst longitudinal portions, which are coupled to the one or more tissueanchors, respectively.

For some applications, the stent is shaped so as to define one or moretension-distributing elements, which (a) extend along at least atension-distribution axial segment of the stent at the one or moretether circumferential locations, respectively, (b) define the one ormore tether interfaces, respectively, and (c) are configured todistribute tension applied by the one or more tethers, respectively,along the tension-distribution axial segment of the stent. For someapplications, the tension-distribution axial segment axially coincideswith the lower-securement axial segment. For some applications, the oneor more tension-distributing elements and the stent are fabricated froma single unit. For some applications, each of the one or moretension-distributing elements has a circumferential arc of between 1 and15 degrees, when the stent is unconstrained in the radially-expandedstate. For some applications, an axial length of each of thetension-distributing elements equals at least 15% of an axial length ofthe stent. For some applications, the axial length of the stent isbetween 20 and 120 mm, and the axial length of each of thetension-distributing elements is between 10 and 120 mm, when the stentis unconstrained in the radially-expanded state.

For some applications, the lower-securement axial segment of the stentextends along at least 30%, such as at least 100%, of an axial length ofthe stent, when the stent is unconstrained in the radially-expandedstate.

For some applications, an interior of the stent defines a right circularcylindrical shape having a radius, and the outward protrusions extendradially outward from the cylindrical shape by a distance equal tobetween 5% and 25% of the radius, when the stent is unconstrained in theradially-expanded state.

For some applications, the one or more tether interfaces are shaped soas to define one or more openings, respectively, through which the oneor more tethers are respectively coupled.

For some applications, each of the one or more tethers includes anelement selected from the group consisting of: one or more metal struts,one or more metal wires, one or more flexible biocompatible textiles,and one or more flexible bands. For some applications, each of the oneor more tethers has a length of between 20 and 120 mm.

For some applications, at least one of the one or more tissue anchorsincludes a helical tissue anchor.

For some applications, the stent is a first stent, and at least one ofthe one or more tissue anchors includes a second generally tubularstent.

For any of the applications described above, the one more tetherinterfaces may include exactly one tether interface at exactly onetether circumferential location, and the one or more tethers may includeexactly one tether having a first longitudinal portion that is coupledto the tether interface. For some applications, the tethercircumferential location is circumferentially centered in thelower-securement circumferential portion. For some applications, thehigher-securement portion extends circumferentially around at least 270degrees of the circumference of the stent, when the stent isunconstrained in the radially-expanded state. For some applications, theexactly one tether interface is shaped so as to define one or moreopenings through which the exactly one tether is coupled.

For any of the applications described above, the outward protrusions maybe rotationally-asymmetrically distributed around the circumference ofthe stent, when the stent is unconstrained in the radially-expandedstate.

For any of the applications described above, the outward protrusions maybe periodically distributed around the higher-securement circumferentialportion, when the stent is unconstrained in the radially-expanded state.

For any of the applications described above, the outward protrusions maybe blunt, when the stent is unconstrained in the radially-expandedstate. Alternatively, for any of the applications described above, theoutward protrusions may be shaped so as to define respective barbs, whenthe stent is unconstrained in the radially-expanded state.

For any of the applications described above, the lower-securementportion may have a circumferential arc that equals at least 200% of anaverage of circumferential distances between circumferential midpointsof circumferentially-adjacent ones of the outward protrusions around thehigher-securement portion, when the stent is unconstrained in theradially-expanded state.

For any of the applications described above, the stent may include aplurality of columnar struts and a plurality of circumferential stentmeanders coupled to the columnar struts at respective axial locations,and one or more of the circumferential stent meanders may be shaped soas to define the outward protrusions at the respective circumferentiallocations around the higher-securement portion, when the stent isunconstrained in the radially-expanded state. For some applications,when the stent is unconstrained in the radially-expanded state, at leastone of the circumferential stent meanders is shaped so as to define (a)around the higher-securement portion, the outward protrusions, and (b)around the lower-securement portion, an arc of a circle if thecircumferential stent meander is projected onto a plane perpendicular toa longitudinal axis of the stent. For some applications, at least one ofthe circumferential stent meanders is shaped so as to define the outwardprotrusions around the higher-securement portion circumferentiallybetween one or more circumferentially-adjacent pairs of the columnarstruts, when the stent is unconstrained in the radially-expanded state.For some applications, at least one of the circumferential stentmeanders is shaped so as to define a plurality of apices, at least someof which are shaped so as to define the outward protrusions, when thestent is unconstrained in the radially-expanded state. For someapplications, respective radii of the columnar struts are measuredbetween respective inner surfaces of the columnar struts and a centrallongitudinal axis of the stent, and an average of respective distancesbetween the central longitudinal axis and respective most-outwardsurfaces of the protrusions equals between 105% and 125% of an averageof the radii, when the stent is unconstrained in the radially-expandedstate.

For any of the applications described above, the higher-securementportion may extend circumferentially around at least 270 degrees of thecircumference of the stent, such as at least 300 degrees, when the stentis unconstrained in the radially-expanded state.

For any of the applications described above, the higher-securementportion may extend circumferentially around no more than 300 degrees ofthe circumference of the stent, when the stent is unconstrained in theradially-expanded state.

There is further provided, in accordance with an application of thepresent invention, apparatus including:

a radially-expandable stent, which, when unconstrained in aradially-expanded state, is generally tubular and shaped so as todefine:

-   -   a plurality of tether interfaces at a plurality of tether        circumferential locations, respectively, each of which tether        interfaces extends circumferentially contiguously around less        than 30 degrees of a circumference of the stent,    -   a plurality of lower-securement portions that extend (a) along        at least respective contiguous lower-securement axial segments        of the stent and (b) circumferentially around respective        contiguous lower-securement circumferential portions of the        stent, wherein (i) each of the lower-securement axial segments        includes one or more of the tether interfaces, (ii) each of the        lower-securement circumferential portions includes one or more        of the tether interfaces, and (iii) the lower-securement        circumferential portions have respective circumferential arcs,        each of which is between 30 and 90 degrees,    -   a plurality of higher-securement portions that extend (a) along        at least respective contiguous higher-securement axial segments        of the stent and (b) circumferentially around respective        higher-securement circumferential portions of the stent,        collectively at all circumferential locations other than those        of the lower-securement circumferential portions, wherein the        lower- and the higher-securement portions alternate around the        stent, and    -   a plurality of outward protrusions at respective circumferential        locations around the higher-securement portions, and not around        the lower-securement portions, such that each of the        higher-securement portions includes one or more of the outward        protrusions;

a plurality of tissue anchors; and

a plurality of tethers having respective first longitudinal portionsthat are coupled to the plurality of tether interfaces, respectively,and respective second longitudinal portions, different from therespective first longitudinal portions, that are coupled the pluralityof tissue anchors, respectively.

For some applications, the circumferential arcs of the lower-securementcircumferential portions are equal to one another.

For some applications, the higher-securement circumferential portionshave respective circumferential arcs that are equal to one another.

For some applications, the circumferential arcs of the lower-securementcircumferential portions are equal to one another, and thehigher-securement circumferential portions have respectivecircumferential arcs that are equal to one another.

For some applications, the stent is shaped so as to define a pluralityof tension-distributing elements, which (a) extend along at leastrespective tension-distribution axial segments of the stent at thetether circumferential locations, respectively, (b) define the tetherinterfaces, respectively, and (c) are configured to distribute tensionapplied by the tethers, respectively, along the tension-distributionaxial segments of the stent, respectively. For some applications, thetension-distribution axial segments axially coincide with thelower-securement axial segments, respectively. For some applications,the tension-distributing elements and the stent are fabricated from asingle unit. For some applications, each of the tension-distributingelements has a circumferential arc of between 1 and 15 degrees, when thestent is unconstrained in the radially-expanded state. For someapplications, an axial length of each of the tension-distributingelements equals at least 15% of an axial length of the stent. For someapplications, the axial length of the stent is between 20 and 120 mm,and the axial length of each of the tension-distributing elements isbetween 10 and 120 mm, when the stent is unconstrained in theradially-expanded state.

For some applications, the lower-securement axial segment of the stentextends along at least 30%, such as at least 100%, of an axial length ofthe stent, when the stent is unconstrained in the radially-expandedstate.

For some applications, an interior of the stent defines a right circularcylindrical shape having a radius, and the outward protrusions extendradially outward from the cylindrical shape by a distance equal tobetween 5% and 25% of the radius, when the stent is unconstrained in theradially-expanded state.

For some applications, the tether interfaces are shaped so as to definerespective one or more openings through which the tethers arerespectively coupled.

For some applications, each of the tethers includes an element selectedfrom the group consisting of: one or more metal struts, one or moremetal wires, one or more flexible biocompatible textiles, and one ormore flexible bands. For some applications, each of the tethers has alength of between 20 and 120 mm.

For some applications, at least one of the tissue anchors includes ahelical tissue anchor.

For some applications, the stent is a first stent, and at least one ofthe tissue anchors includes a second generally tubular stent.

For any of the applications described above, the stent, whenunconstrained in the radially-expanded state, may be shaped so as todefine a same number of the tether interfaces and the lower-securementportions. For some applications, the tether circumferential locationsare circumferentially centered in the lower-securement portions,respectively.

For any of the applications described above, the outward protrusions maybe rotationally-asymmetrically distributed around the circumference ofthe stent, when the stent is unconstrained in the radially-expandedstate.

For any of the applications described above, the outward protrusions maybe periodically distributed around each of the higher-securementcircumferential portions, when the stent is unconstrained in theradially-expanded state.

For any of the applications described above, the outward protrusions maybe blunt, when the stent is unconstrained in the radially-expandedstate. Alternatively, for any of the applications described above, theoutward protrusions may be shaped so as to define respective barbs, whenthe stent is unconstrained in the radially-expanded state.

For any of the applications described above, each of the circumferentialarcs of the lower-securement circumferential portions may equal at least200% of an average of circumferential distances between circumferentialmidpoints of circumferentially-adjacent ones of the outward protrusionsaround the higher-securement portions, when the stent is unconstrainedin the radially-expanded state.

For any of the applications described above, the stent may include aplurality of columnar struts and a plurality of circumferential stentmeanders coupled to the columnar struts at respective axial locations,and one or more of the circumferential stent meanders may be shaped soas to define the outward protrusions at the respective circumferentiallocations around the higher-securement portions, when the stent isunconstrained in the radially-expanded state. For some applications,when the stent is unconstrained in the radially-expanded state, at leastone of the circumferential stent meanders is shaped so as to define (a)around the higher-securement portions, the outward protrusions, and (b)around the lower-securement portions, respective arcs of a circle if thecircumferential stent meander is projected onto a plane perpendicular toa longitudinal axis of the stent. For some applications, at least one ofthe circumferential stent meanders is shaped so as to define the outwardprotrusions around the higher-securement portions circumferentiallybetween one or more circumferentially-adjacent pairs of the columnarstruts, when the stent is unconstrained in the radially-expanded state.For some applications, at least one of the circumferential stentmeanders is shaped so as to define a plurality of apices, at least someof which are shaped so as to define the outward protrusions, when thestent is unconstrained in the radially-expanded state. For someapplications, respective radii of the columnar struts are measuredbetween respective inner surfaces of the columnar struts and a centrallongitudinal axis of the stent, and an average of respective distancesbetween the central longitudinal axis and respective most-outwardsurfaces of the protrusions equals between 105% and 125% of an averageof the radii, when the stent is unconstrained in the radially-expandedstate.

The present invention will be more fully understood from the followingdetailed description of embodiments thereof, taken together with thedrawings, in which:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration of an anchoring system, in accordancewith an application of the present invention;

FIGS. 2A-D are schematic views of a stent of the anchoring system ofFIG. 1, in accordance with an application of the present invention;

FIGS. 3A-B are schematic illustrations of another configuration of theanchoring system of FIG. 1, in accordance with an application of thepresent invention;

FIGS. 4A-B are schematic illustrations of another radially-expandablestent, in accordance with an application of the present invention;

FIGS. 5A-D are schematic illustrations of an exemplary deployment of theanchoring system of FIG. 1 for repairing a tricuspid valve, inaccordance with some applications of the present invention;

FIGS. 6A-B are schematic illustrations of yet anotherradially-expandable stent, in accordance with an application of thepresent invention; and

FIGS. 7A-B are schematic illustrations of a barbed configuration of theanchoring system of FIG. 1, in accordance with an application of thepresent invention.

DETAILED DESCRIPTION OF APPLICATIONS

FIG. 1 is a schematic illustration of an anchoring system 10, inaccordance with an application of the present invention. Anchoringsystem 10 comprises a radially-expandable stent 20, and typically one ormore tissue anchors 30 and one or more tethers 34 that connect the stentto the one or more tissue anchors. Stent 20 is configured to beimplanted in a body lumen, such as a blood vessel. For someapplications, anchoring system 10 is used for repairing anatrioventricular valve of a patient using tension, such as describedhereinbelow with reference to FIGS. 5A-D. For these applications, one ormore tissue anchors 30 are implantable in a vicinity of theatrioventricular valve, and stent 20 is expanded in a portion of a bloodvessel, e.g., a superior vena cava, an inferior vena cava, a coronarysinus, or a hepatic vein, e.g., the left hepatic vein, the right hepaticvein, or the middle hepatic vein.

Reference is still made to FIG. 1, and is additionally made to FIGS.2A-D, which are schematic views of stent 20, in accordance with anapplication of the present invention. FIGS. 2A-B are side-views of stent20. For sake of illustration, FIG. 2C shows stent 20 in a flattenedstate, in which stent 20, when unconstrained in a radially-expandedstate, has been cut longitudinally and flattened. It is noted thatbecause of the particular flattened view in FIG. 2C, outward protrusions70, described below, are not visible; these protrusions are in factpresent. FIG. 2D is an end-view of stent 20.

Stent 20 typically comprises a plurality of interconnected superelasticmetallic struts 40. Stent 20 may be manufactured by expanding alaser-slotted metallic tube, by chemically etching a flat sheet, byshaping a single wire, by assembling individual wire elements, or by anyother method of construction known in the art. Stent 20 typicallycomprises a metal, such as a shape-memory alloy, e.g., Nitinol.

Stent 20, when unconstrained in a radially-expanded state (i.e., noforces are applied to the stent by a delivery tool, wall of a bodyvessel, or otherwise), such as shown in FIGS. 1 and 2A-D, is generallytubular and shaped so as to define:

-   -   one or more tether interfaces 50 at one or more tether        circumferential locations 52, respectively, each of which tether        interfaces 50 extends circumferentially contiguously around less        than 30 degrees of a circumference C of stent 20 (labeled in        FIG. 2C). In the configuration shown in FIGS. 1 and 2A-D, stent        20 is shaped so as to define exactly one tether interface 50 at        exactly one tether circumferential location 52, which extends        circumferentially contiguously around less than 30 degrees of        circumference C of stent 20;    -   a lower-securement portion 56 that extends (a) along at least a        contiguous lower-securement axial segment 58 of stent 20        (labeled in FIGS. 2A and 2C) and (b) circumferentially around a        contiguous lower-securement circumferential portion 60 of stent        20, which lower-securement axial segment 58 and lower-securement        circumferential portion 60 include the one or more tether        interfaces 50 (e.g., exactly one tether interface 50, as shown        in FIGS. 1 and 2A-D). Typically, lower-securement axial segment        58 extends along at least 30%, e.g., at least 70%, or 100% (as        shown), of an axial length L1 of stent 20;    -   a higher-securement portion 64 that extends (a) along at least a        contiguous higher-securement axial segment 65 and (b)        circumferentially around a higher-securement circumferential        portion 66 of stent 20 at all circumferential locations other        than those of lower-securement circumferential portion 60.        Higher-securement circumferential portion 66 typically extends        around at least 215 degrees of circumference C (e.g., at least        270 degrees, or at least 300 degrees), no more than 330 degrees        of circumference C (e.g., no more than 300 degrees), and/or        between 215 and 330 degrees of circumference C (e.g., between        270 and 330 degrees, such as between 300 and 330 degrees, or        between 270 and 300 degrees); and    -   a plurality of outward protrusions 70 at respective outward        circumferential locations 72 around higher-securement portion        64, and not around lower-securement portion 56.

Outward protrusions 70 of higher-securement portion 64 causehigher-securement portion 64 to apply greater securement forces againstthe body lumen wall than applied by lower-securement portion 56, whichlacks outward protrusions. Such selective securement allows relativeaxial reciprocating movement of struts 40 of lower-securement portion56, while maintaining the stent as a whole secured in the body lumen.Such selective securement may thus relieve stresses in the stent frameresulting from cyclic loads applied to the stent (e.g., cyclic cardiacloads) at the one or more tether circumferential locations 52, therebyon the one hand enabling higher fatigue endurance in the stent, while onthe other hand reducing the risk of stent migration.

Each of outward protrusions 70 is shaped so as to include a radiallyoutward directional component. Optionally, each of the protrusions isshaped so as to additionally include an axial directional component,i.e., to point toward one end of the stent, typically pointing againstthe direction of axial force.

For some applications, as shown in FIGS. 1 and 2A-D, outward protrusions70 are rotationally-asymmetrically distributed around circumference C ofstent 20, when stent 20 is unconstrained in the radially-expanded state.Alternatively or additionally, for some applications, also as shown inFIGS. 1 and 2A-D, outward protrusions 70 are periodically distributedaround higher-securement circumferential portion 66, when stent 20 isunconstrained in the radially-expanded state.

Typically, as shown in FIGS. 1 and 2A-D, outward protrusions 70 areblunt, when stent 20 is unconstrained in the radially-expanded state.Alternatively, outward protrusions 70 are shaped so as to definerespective barbs 530, when stent 20 is unconstrained in theradially-expanded state, such as described hereinbelow with reference toFIGS. 7A-B.

For some applications, an axial length of lower-securement axial segment58 is greater than an axial length of higher-securement axial segment65, such as at least 10% greater, e.g., at least 30% or at least 50%greater. Typically, lower-securement axial segment 58 andhigher-securement axial segment 65 partially axially overlap. For someapplications, higher-securement axial segment 65 is aligned entirelyaxially within lower-securement axial segment 58 (although notcircumferentially aligned therewith).

For some applications (configuration not shown), stent 20 includes asecurement portion that does not axially overlap with eitherlower-securement axial segment 58 or higher-securement axial segment 65,and is typically located near the end of stent 20 opposite the endnearest the one or more tether interfaces 50.

For some applications, struts 40 are shaped so as to define a pluralityof columnar struts 74 and a plurality of circumferential stent meanders76 (defining a plurality of apices), coupled to columnar struts 74 atrespective axial locations. Typically, each of circumferential stentmeanders 76 is disposed around the entire circumference C of stent 20.For example, as perhaps may best seen in FIG. 2C, stent 20 may haveeight circumferential stent meanders 76 and 14 columnar struts 74. It isto be understood that other configurations are possible, with any numberof circumferential stent meanders 76. Typically, stent 20 comprisesbetween three circumferential stent meanders 76 (for short stents, e.g.,for a valve frame) and 20 circumferential stent meanders 76 (for longstents, e.g., for stent-grafts for treating abdominal aortic aneurisms(“AAAs”)), and any number of columnar struts 74, typically between sixand 20.

A set 80 of one or more of circumferential stent meanders 76 are shapedso as to define outward protrusions 70 at respective outwardcircumferential locations 72 around higher-securement portion 64, whenstent 20 is unconstrained in the radially-expanded state. For someapplications, each of circumferential stent meanders 76 of set 80defines a number of outward protrusions 70 equal to between 20% and 100%of the total number of apices of the stent meander around the entirecircumference C of the stent, such as between 50% and 90%, e.g., 86%(12/14). For some applications, each of circumferential stent meanders76 of set 80 defines between 3 and 20 of outward protrusions 70, such asbetween 6 and 14 of outward protrusions 70, e.g., 12 of outwardprotrusions.

For some applications, when stent 20 is unconstrained in theradially-expanded state, at least one of circumferential stent meanders76 is shaped so as to define:

-   -   around higher-securement portion 64, outward protrusions 70 (the        circumferential stent meander may thus define a polygon if        projected onto a plane perpendicular to a longitudinal axis 82        of stent 20); and    -   around lower-securement portion 56, an arc of a circle if the        circumferential stent meander is projected onto the plane        perpendicular to longitudinal axis 82 of stent 20.        For some applications, exactly one, exactly two, exactly three        (as shown), exactly four, or five or more of circumferential        stent meanders 76 are thus shaped. For example, first, third,        and fifth distal circumferential stent meanders 76A, 76C, and        76E include:    -   respective portions around higher-securement portion 64, which        define outward protrusions 70 (and thus define respective        polygons if projected onto the plane perpendicular to        longitudinal axis 82 of stent 20), and    -   respective portions around lower-securement portion 56, which do        not define outward protrusions 70 (and thus define respective        arcs of a circle if projected onto the plane perpendicular to        longitudinal axis 82 of stent 20).        In contrast, second, fourth, sixth, seventh, and eighth        circumferential stent meanders 76B, 76D, 76F, 76G, and 76H do        not define outward protrusions 70, and thus define respective        circles if projected onto the plane perpendicular to        longitudinal axis 82 of stent 20. Stent 20 may be shaped to        define other polygon-circular shape patterns (e.g., every x        circumferential stent meanders 76 may define outward        protrusions, such as every second meander, or every third        meander). For some applications, lower-securement portion 56 is        generally shaped as a circumferential portion of a circular        cylinder. Such providing of lower-securement axial spaces        between circumferential stent meanders may facilitate better        fatigue resistance. In addition, the securement is provided by a        plurality of circumferential stent meanders 76 at a respective        plurality of axial locations, rather than only by a single row        at one end of the stent, or single rows at each end of the        stent, as in some conventional stents.

For some applications, when stent 20 is unconstrained in theradially-expanded state, at least one of circumferential stent meanders76 is shaped so as to define outward protrusions 70 aroundhigher-securement portion 64 circumferentially between one or morecircumferentially-adjacent pairs 84 of columnar struts 74, such asbetween every circumferentially-adjacent pair of columnar struts 74around higher-securement portion 64, as shown). For some applications,exactly one, exactly two, exactly three (as shown and described above),exactly four, or five or more of circumferential stent meanders 76 arethus shaped.

For some applications, outward protrusions 70 are cascaded aroundhigher-securement portion 64.

For some applications, at least one of circumferential stent meanders 76is shaped so as to define a plurality of apices 86, at least some ofwhich are shaped so as to define outward protrusions 70, when stent 20is unconstrained in the radially-expanded state.

For some applications, when stent 20 is unconstrained in theradially-expanded state, respective radii R of columnar struts 74 aremeasured between respective inner surfaces of columnar struts 74 andcentral longitudinal axis 82 of the stent. An average of respectivedistances D1 between respective most-outward surfaces 88 of outwardprotrusions 70 equals between 105% and 125% of an average of radii R.For applications in which stent 20 is shaped generally as a circularcylinder, radii R equal one another, and distances D1 typically equalone another. Alternatively or additionally, for some applications, whenstent 20 is unconstrained in the radially-expanded state, outwardprotrusions 70 have a length P of at least 1 mm, no more than 5 mm,and/or between 1 and 5 mm, measured from an outer surface 90 of stent 20other than at the protrusions. Further alternatively or additionally,for some applications, wherein an interior of stent 20 defines a rightcircular cylindrical shape having radius R, and outward protrusions 70extend radially outward from the cylindrical shape by a distance equalto between 5% and 25% of radius R, when stent 20 is unconstrained in theradially-expanded state.

The dimensions of stent 20 may vary in order to fit the body lumen inwhich it is placed, according to the medical application. Typically,when unconstrained in the radially-expanded state, stent 20 has (a) aninner diameter D2 that equals about 10-30% larger than the innerdiameter of the body lumen, and/or (b) axial length L1 that equalsbetween 100% and 600% of inner diameter D2. For example, forapplications in which stent 20 is configured to be implanted a vena cavafor tethering anchor 30 at the tricuspid valve, such as describedhereinbelow with reference to FIGS. 5A-D, (a) inner diameter D2 may beat least 25 mm, no more than 60 mm, and/or between 25 and 60 mm, (b)stent length L1 may be at least 25 mm, no more than 100 mm, and/orbetween 25 and 100 mm, and (c) protrusion length P may be 3 mm. Forapplications in which stent 20 is configured to be implanted in theabdominal aorta, (a) inner diameter D2 may be at least 30 mm, no morethan 50 mm, and/or between 30 and 50 mm, (b) stent length L1 may be atleast 50 mm, no more than 300 mm, and/or between 50 and 300 mm, and (c)protrusion length P may be 5 mm. For some applications, stent length L1is at least 20 mm, no more than 120 mm, and/or between 20 and 120 mm,when stent 20 is unconstrained in the radially-expanded state.

Typically, inner diameter D2 is constant along the stent, i.e., thestent is not flared at either end.

For some applications, stent 20 is shaped so as to define one or more(e.g., exactly one) tension-distributing elements 94, which (a) extendalong at least a tether-distribution axial segment 95 of stent 20 at theone or more tether circumferential locations 52, respectively, (b)define the one or more tether interfaces 50, respectively, and (c) areconfigured to distribute tension applied by the one or more tethers 34,respectively, along tether-distribution axial segment 95. For someapplications, as shown, tether-distribution axial segment 95 axiallycoincides with lower-securement axial segment 58. Optionally, the one ormore tension-distributing elements 94 and stent 20 are fabricated from asingle unit.

For some applications, each of the one or more tension-distributingelements 94 has a circumferential arc A1 (labeled in FIG. 2C) of atleast 1 degree, no more than 15 degrees, and/or between 1 and 15 degreeswhen stent 20 is unconstrained in the radially-expanded state. For someapplications, an axial length L2 of each of tension-distributingelements 94 equals at least 15% of axial length L1 of stent 20, such asat least 75% of axial length L1 of stent 20. For some applications, suchas when stent length L1 is at least 20 mm, no more than 120 mm, and/orbetween 20 and 120 mm, axial length L2 of each of tension-distributingelements 94 is at least 10 mm, no more than 120, and/or between 10 and120 mm, when stent 20 is unconstrained in the radially-expanded state.

For some applications, lower-securement portion 56 has a circumferentialarc A2 that equals at least 150% (e.g., at least 200%) of an average ofcircumferential distances D3 between circumferential midpoints 96 ofcircumferentially-adjacent ones 98 of outward protrusions 70 aroundhigher-securement portion 64, when stent 20 is unconstrained in theradially-expanded state.

Reference is again made to FIG. 1. The one or more tethers 34 haverespective first longitudinal portions 100 that are coupled to the oneor more tether interfaces 50, respectively, and respective secondlongitudinal portions 102, different from respective first longitudinalportions 100, which are coupled to the one or more tissue anchors 30,respectively. For some applications, the one or more tether interfaces50 are shaped so as to define one or more openings 104, respectively,through which the one or more tethers 34 are respectively coupled.

For some applications, each of the one or more tethers 34 comprises anelement selected from the group consisting of: one or more metal struts,one or more metal wires, one or more flexible biocompatible textiles,and one or more flexible bands. For some applications, each of the oneor more tethers 34 has a length of at least 20 mm, no more than 120 mm,and/or between 20 and 120 mm.

For some applications, at least one of the one or more tissue anchors 30comprises a helical tissue anchor. For some applications, the helicaltissue anchor comprises a generally helical shaftless tissue-couplingelement 106 and, typically, a proximal head 108. For some applications,such as described in U.S. Provisional Application 61/750,427, filed Jan.9, 2013, which is assigned to the assignee of the present applicationand is incorporated herein by reference, helical tissue-coupling element106 has (a) a first axial thickness along a first axial portion of ashaftless helical portion of the helical tissue-coupling element, and(b) a second axial thickness along a second axial portion of theshaftless helical portion more distal than the first axial portion. Thesecond axial thickness is greater than the first axial thickness. Thefirst and second axial thicknesses are measured along a longitudinalaxis of the helical tissue-coupling element. Alternatively oradditionally, the helical tissue-coupling element has (a) a first axialyield strength along the first axial portion, and (b) a second axialyield strength along the second axial portion (more distal than thefirst axial portion). The second axial yield strength is greater thanthe first axial yield strength. Further alternatively or additionally,the helical tissue-coupling element has (a) a first axial stiffnessalong the first axial portion, and (b) a second axial stiffness alongthe second axial portion (more distal than the first axial portion). Thesecond axial stiffness is greater than the first axial stiffness.

For some applications, such as described in the above-mentioned '427application, the helical tissue-coupling element 106 is shaped so as todefine (a) a first surface along a first axial surface characteristicportion of the shaftless helical portion of the helical tissue-couplingelement, which first surface has a first surface characteristic, and (b)a second surface along a second axial surface characteristic portion ofthe shaftless helical portion different from the first axial surfacecharacteristic portion. The second surface has a second surfacecharacteristic that is configured to inhibit rotation of the helicaltissue-coupling element to a greater extent than does the first surfacecharacteristic. The first surface characteristic may, for example, be ahigh level of smoothness.

For some applications, stent 20 is a first stent, and at least one ofthe one or more tissue anchors 30 comprises a second generally tubularstent. A similar two-stent configuration (albeit without the stentconfigurations described herein) is shown, for example, in FIG. 4C ofPCT Publication WO 2013/011502, which is incorporated herein byreference. For some applications, the second stent is expanded in aportion of a second blood vessel of the patient, e.g., the superior venacava, the inferior vena cava, the coronary sinus, or a hepatic vein,e.g., the left hepatic vein, the right hepatic vein, or the middlehepatic vein.

For some applications, as shown in FIGS. 1 and 2A-D, the one more tetherinterfaces 50 comprise exactly one tether interface 50 at exactly onetether circumferential location 52, and the one or more tethers 34comprise exactly one tether 34 having a first longitudinal portion thatis coupled to the tether interface. In some of these applications,higher-securement portion 64 extends circumferentially around at least270 degrees of circumference C of stent 20, when stent 20 isunconstrained in the radially-expanded state.

For some applications, tether circumferential location 52 iscircumferentially centered in lower-securement circumferential portion60, as shown in FIGS. 2A-D. Alternatively, tether circumferentiallocation 52 is not circumferentially centered in lower-securementcircumferential portion 60 (configuration not shown). For someapplications, the exactly one tether interface is shaped so as to definethe one or more openings 104 through which the exactly one tether iscoupled.

Reference is now made to FIGS. 3A-B, which are schematic illustrationsof another configuration of anchoring system 10, in accordance with anapplication of the present invention. In this configuration, anchoringsystem 10 comprises a radially-expandable stent 120, which is oneconfiguration of stent 20 described hereinabove with reference to FIGS.1 and 2A-D. As mentioned above, anchoring system 10 typically comprisesone or more tissue anchors 30 and one or more tethers 34 that connectthe stent to the one or more tissue anchors. Also as mentioned above,stent 20, when unconstrained in the radially-expanded state (i.e., noforces are applied to the stent by a delivery tool, wall of a bodyvessel, or otherwise), is shaped so as to define one or more tetherinterfaces 50 at one or more tether circumferential locations 52,respectively.

In the configuration shown in FIGS. 3A-B, anchoring system comprises twotissue anchors 30 and two tethers 34 that connect stent 120 to the twotissue anchors, respectively. Stent 120 is shaped so as to define twotether interfaces 50 at two tether circumferential locations 52,respectively, each of which extends circumferentially contiguouslyaround less than 30 degrees of circumference C of stent 20. Two tethers34 have respective first longitudinal portions 100 that are coupled totwo tether interfaces 50, respectively, and two respective secondlongitudinal portions 102, different from respective first longitudinalportions 100, which are coupled to two tissue anchors 30, respectively.

This configuration may be useful for applying tension to two sites towhich the two anchors are coupled, such as two sites of the tricuspidvalve. For example, this configuration may be used in combination withthe anchor placement described with reference to, and shown in, FIG. 2Band/or FIG. 3B of above-mentioned PCT Publication WO 2013/011502,mutatis mutandis.

Reference is now made to FIGS. 4A-B, which are schematic illustrationsof another radially-expandable stent 220, in accordance with anapplication of the present invention. FIGS. 4A and 4B are side- andend-views of stent 220, respectively. In this configuration, anchoringsystem 10 comprises radially-expandable stent 220, a plurality (e.g.,two) of tissue anchors 30 and a plurality (e.g., two) of tethers 34 thatconnect the stent to the one or more tissue anchors. Other than asdescribed below, stent 220 may have any of the features of stent 20,described hereinabove with reference to FIGS. 1 and 2A-D.

Stent 220 typically comprises a plurality of interconnected superelasticmetallic struts 40, and may be manufactured as described hereinaboveregarding stent 20. Stent 220, when unconstrained in a radially-expandedstate (i.e., no forces are applied to the stent by a delivery tool, wallof a body vessel, or otherwise), such as shown in FIGS. 4A-D, isgenerally tubular and shaped so as to define:

-   -   a plurality of tether interfaces 50 at a plurality of tether        circumferential locations 52, respectively, each of which tether        interfaces 50 extends circumferentially contiguously around less        than 30 degrees of a circumference of stent 220. In the        configuration shown in FIGS. 4A-B, stent 220 is shaped so as to        define two tether interfaces 50 at two tether interface        locations 52;    -   a plurality of lower-securement portions 56 that extend (a)        along at least respective contiguous lower-securement axial        segments 58 of stent 220 and (b) circumferentially around        respective contiguous lower-securement circumferential portions        60 of stent 220. Each of lower-securement axial segments 58        includes one or more of tether interfaces 50 (e.g., exactly one        of tether interfaces 50, as shown in FIGS. 4A-B). Each of        lower-securement circumferential portions 60 includes one or        more of tether interfaces 50 (e.g., exactly one of tether        interfaces 50, as shown in FIGS. 4A-B). Lower-securement        portions 56 have respective circumferential arcs, each of which        typically is between 30 and 90 degrees;    -   a plurality of higher-securement portions 64 that extend (a)        along at least respective contiguous higher-securement axial        segments 65 and (b) circumferentially around respective        higher-securement circumferential portions 66 of stent 220,        collectively at all circumferential locations other than those        lower-securement circumferential portions 60. Lower- and        higher-securement portions 56 and 64 alternate around stent 220        (such that there are an equal number of lower- and        higher-securement portions 56 and 64); and    -   a plurality of outward protrusions 70 at respective outward        circumferential locations 72 around higher-securement portions        64, and not around lower-securement portions 56, such that each        of higher-securement portions 64 includes one or more of outward        protrusions 70.

Outward protrusions 70 of higher-securement portion 64 causehigher-securement portion 64 to apply greater securement forces againstthe body lumen wall than applied by lower-securement portion 56, whichlacks outward protrusions. Such selective securement allows relativeaxial reciprocating movement of struts 40 of lower-securement portion56, while maintaining the stent as a whole secured in the body lumen.Such selective securement may thus relieve stresses in the stent frameresulting from cyclic loads applied to the stent (e.g., cyclic cardiacloads) at tether circumferential locations 52, thereby enabling higherfatigue endurance in the stent.

For some applications, the circumferential arcs of lower-securementcircumferential portions 60 are equal to one another. Alternatively oradditionally, for some applications, higher-securement circumferentialportions 66 have respective circumferential arcs that are equal to oneanother.

For some applications, stent 220, when unconstrained in theradially-expanded state, is shaped so as to define a same number oftether interfaces 50 and lower-securement portions 56. For someapplications, tether circumferential locations 52 are circumferentiallycentered in lower-securement circumferential portions 60, respectively,as shown in FIGS. 4A-B. Alternatively, tether circumferential locations52 are not circumferentially centered in lower-securementcircumferential portions 60, respectively (configuration not shown).

For some applications, struts 40 are shaped so as to define theplurality of columnar struts 74 and the plurality of circumferentialstent meanders 76 coupled to columnar struts 74 at respective axiallocations. Typically, each of circumferential stent meanders 76 isdisposed around the entire circumference of stent 220. For someapplications, when stent 220 is unconstrained in the radially-expandedstate, at least one of circumferential stent meanders 76 is shaped so asto define (a) around higher-securement portions 64, outward protrusions70, and (b) around lower-securement portions 56, respective arcs of acircle if the circumferential stent meander is projected onto a planeperpendicular to longitudinal axis 82 of stent 220.

As mentioned above, stent 220 may have any of the features of stent 20,described hereinabove with reference to FIGS. 1 and 2A-D. Such featuresinclude, but are not limited to, (a) a plurality of tension-distributingelements 94, which are configured to distribute tension applied bytethers 34, respectively, along the axial portion of stent 220, (b) therotationally asymmetric distribution of outward protrusions 70 aroundthe circumference of stent 220, when stent 220 is unconstrained in theradially-expanded state, and (c) the periodic distribution of outwardprotrusions 70 around each of higher-securement circumferential portions66, when stent 220 is unconstrained in the radially-expanded state.

The configuration described with reference to FIGS. 4A-B may be usefulfor applying tension to two sites to which the two anchors are coupled,such as two sites of the tricuspid valve. For example, thisconfiguration may be used in combination with the anchor placementdescribed with reference to, and shown in, FIG. 2B and/or FIG. 3B ofabove-mentioned PCT Publication WO 2013/011502, mutatis mutandis.

Reference is now made to FIGS. 5A-D, which are schematic illustrationsof an exemplary deployment of anchoring system 10 for repairing atricuspid valve 304 of a heart 302 of a patient, in accordance with someapplications of the present invention. Although FIGS. 5A-D show thedeployment of stent 20, described hereinabove with reference to FIGS. 1and 2A-D, the same techniques, mutatis mutandis, may be used fordeploying stent 120, described hereinabove with reference to FIGS. 3A-B,stent 220, described hereinabove with reference to FIGS. 4A-B, and stent420, described hereinbelow with reference to FIGS. 6A-B.

System 10 is used for adjusting a distance between first and secondimplantation sites by pulling to apply tension to or relaxing tether 34and/or by applying tension to at least one of tissue anchor 30 and stent20. Responsively, a distance between the leaflets of tricuspid valve 304is adjusted to reduce and eliminate regurgitation through valve 304, andthereby, valve 304 is repaired. For some applications, tether 34 ispulled or relaxed by manipulating stent 20, as is described hereinbelow.

For some applications, stent 20 is advanced toward and expanded in aportion of an inferior vena cava 308 (such as shown in FIGS. 5A-D) or asuperior vena cava 310 (such as shown in FIGS. 1E-G of theabove-mentioned '601 publication), i.e., a blood vessel that is indirect contact with a right atrium 306 of heart 302.

FIG. 5A shows the advancement of a catheter 322 toward atrium 306 untila distal end 323 of the catheter is disposed within atrium 306. Theprocedure is typically performed with the aid of imaging, such asfluoroscopy, transesophageal echo, and/or echocardiography. For someapplications, the procedure begins by advancing a semi-rigid guidewireinto right atrium 306 of the patient. The guidewire provides a guide forthe subsequent advancement of catheter 322 therealong and into the rightatrium. Catheter 322 typically comprises a 14-20 F sheath, although thesize may be selected as appropriate for a given patient. Catheter 322 isadvanced through vasculature into right atrium 306 using a suitablepoint of origin typically determined for a given patient, such asdescribed in PCT Publication WO 2011/089601, which is assigned to theassignee of the present application and is incorporated herein byreference.

Once distal end 323 of catheter 322 is disposed within atrium 306, ananchor-deployment tube 324 is extended from within catheter 322 beyonddistal end 323 thereof and toward a first implantation site 330.Anchor-deployment tube 324 holds tissue anchor 30 and a distal portionof tether 34. For some applications, tube 324 is steerable, as is knownin the catheter art, while for other applications, a separate steerableelement may be coupled to anchor-deployment tube 324. Under the aid ofimaging guidance, anchor-deployment tube 324 is advanced toward firstimplantation site 330 until a distal end thereof contacts cardiac tissueof heart 302 at first implantation site 330. Anchor-deployment tube 324facilitates atraumatic advancement of tissue anchor 30 toward firstimplantation site 330. For such applications in which anchor-deploymenttube 324 is used, stent 20 is compressed within a portion of tube 324.

As shown, first implantation site 330 comprises a portion of an annulusof tricuspid valve 304. Implantation site 330 typically comprises aportion of the annulus of valve 304 that is between (1) the middle ofthe junction between the annulus and anterior leaflet 314, and (2) themiddle of the junction between the annulus and posterior leaflet 316,e.g., between the middle of the junction between the annulus andanterior leaflet 314 and the commissure between the anterior andposterior leaflets. That is, tissue anchor 30 is coupled to, e.g.,screwed into, the fibrous tissue of the tricuspid annulus close to thecommissure in between anterior leaflet 314 and posterior leaflet 316.Implantation site 330 is typically close to the mural side of valve 304.For such applications, the drawing together of first and secondimplantation sites 330 and 352 cinches valve 304 and may create abicuspidization of tricuspid valve 304, and thereby achieve strongercoaptation between anterior leaflet 314 and septal leaflet 312.

As shown in FIG. 5B, an anchor-manipulating tool (not shown for clarityof illustration), which is slidably disposed within anchor-deploymenttube 324, is slid distally within tube 324 so as to push distally tissueanchor 30 and expose tissue anchor 30 from within tube 324. For someapplications of the present invention, the anchor-manipulating tool isreversibly coupled to tissue anchor 30 and facilitates implantation oftissue anchor 30 in the cardiac tissue.

The physician rotates the anchor-manipulating tool from a site outsidethe body of the patient in order to rotate tissue anchor 30 and therebyscrew at least a portion of tissue anchor 30 in the cardiac tissue.Alternatively, system 320 is provided independently of theanchor-manipulating tool, and anchor-deployment tube 324 facilitatesimplantation of tissue anchor 30 in the cardiac tissue. The physicianrotates anchor-deployment tube 324 from a site outside the body of thepatient in order to rotate tissue anchor 30 and thereby screw at least aportion of tissue anchor 30 in the cardiac tissue.

As shown in FIG. 5C, following the implantation of tissue anchor 30 atfirst implantation site 330, anchor-deployment tube 324 is retractedwithin catheter 322 in order to expose tether 34. Subsequently, tether34 is tensioned in order to repair tricuspid valve 304, as describedhereinbelow.

For some applications, prior to pulling the portion of tether 34 that isdisposed between tissue anchor 30 and distal end 323 of catheter 322, amechanism that facilitates the application of a pulling force to tether34 is fixed in place, as described in the above-mentioned '601publication.

For some applications, catheter 322 is reversibly coupled to a proximalportion of tether 34 by being directly coupled to the proximal portionof tether 34 and/or catheter 322 is reversibly coupled to stent 20. Forexample, catheter 322 may be reversibly coupled to stent 20 by thestent's application of a radial force against the inner wall of catheter322 because of the tendency of stent 20 to expand radially. Followingimplantation of tissue anchor 30, catheter 322 (or an element disposedtherein) is then pulled proximally to apply tension to tether 34, which,in such an application, functions as a tensioning element. For someapplications, catheter 322 pulls on stent 20 in order to pull tether 34.For other applications, catheter 322 pulls directly on tether 34. Foryet other applications, a pulling mechanism pulls on tether 34, as isdescribed with reference to FIGS. 5A-D in the above-referenced '601publication.

Pulling tether 34 pulls taut the portion of tether 34 that is disposedbetween tissue anchor 30 and distal end 323 of catheter 322.Responsively to the pulling of tether 34, at least the anterior andseptal leaflets of tricuspid valve 304 are drawn together because thegeometry of the annulus and/or of the wall of atrium 306 is altered inaccordance with the pulling of tether 34 and depending on thepositioning of tissue anchor 30.

For some applications, during the pulling of tether 34 by catheter 322,a level of regurgitation of tricuspid valve 304 is monitored. Tether 34is pulled until the regurgitation is reduced or ceases. Once thephysician determines that the regurgitation of valve 304 is reduced orceases, and valve 304 has been repaired, the physician decouplescatheter 322 from stent 20 disposed therein and/or from tether 34, andthen retracts catheter 322 in order to expose stent 20. During theadvancement of catheter 322 toward atrium 306, stent 20 is disposedwithin a distal portion of catheter 322 in a compressed state. Followinginitial retracting of catheter 322, stent 20 is exposed and is allowedto expand and contact a wall of inferior vena cava 308.

FIG. 5D shows stent 20 fully exposed and fully expanded, and thusimplanted in inferior vena cava 308. Stent 20 maintains the tension oftether 34 on tissue anchor 30 and thereby on the portion of cardiactissue to which tissue anchor 30 is coupled.

The techniques described with reference to FIGS. 5A-B may be performedin combination with techniques described in the above-mentioned '601publication, mutatis mutandis.

As described above, for some applications the techniques describedherein are used to repair the tricuspid valve. The techniques describedherein may also be used to repair the mitral valve of the patient,mutatis mutandis.

Reference is now made to FIGS. 6A-B, which are schematic illustrationsof another radially-expandable stent 420, in accordance with anapplication of the present invention. FIGS. 6A and 6B are side- andend-views of stent 420, respectively. In this configuration, anchoringsystem 10 comprises radially-expandable stent 420, one or more tissueanchors 30, and one or more tethers 34 that connect the stent to the oneor more tissue anchors. Other than as described below, stent 420 mayhave any of the features of stent 20, described hereinabove withreference to FIGS. 1 and 2A-D, stent 120, described hereinabove withreference to FIGS. 3A-D, and/or stent 220, described hereinabove withreference to FIGS. 4A-D.

Unlike stents 20, 120, and 220, stent 420 is not shaped so as to definelower-securement portion 56. Thus, the portion of stent 420 thatincludes one or more tether interfaces 50 (e.g., exactly one tetherinterface 50) at one or more tether circumferential locations 52 (e.g.,at exactly one tether circumferential location 52) provides the samelevel of securement to the body lumen as do the other portions of thestent.

When stent 420 is unconstrained in the radially-expanded state (i.e., noforces are applied to the stent by a delivery tool, wall of a bodyvessel, or otherwise), only a portion of circumferential stent meanders76 (e.g., exactly one, exactly two, exactly three (as shown), exactlyfour, or five or more of circumferential stent meanders 76) are shapedso as to define one or more outward protrusions. For example, first,third, and fifth distal circumferential stent meanders 76A, 76C, and 76Emay define outward protrusions 70, and thus define respective polygonsif projected onto the plane perpendicular to longitudinal axis 82 ofstent 420. In contrast, the other circumferential stent meanders may notdefine any outward protrusions 70, and thus define respective circles ifprojected onto the plane perpendicular to longitudinal axis 82 of stent420. Stent 420 may be shaped to define other polygon-circular shapepatterns (e.g., every x circumferential stent meanders 76 may defineoutward protrusions, such as every second meander, or every thirdmeander). Such providing of lower-securement axial spaces betweencircumferential stent meanders may facilitate better tissue fixation byscattering the protrusions.

For some applications, when stent 420 is unconstrained in theradially-expanded state, at least one of circumferential stent meanders76 is shaped so as to define outward protrusions 70 circumferentiallybetween one or more circumferentially-adjacent pairs 84 of columnarstruts 74, such as between every circumferentially-adjacent pair ofcolumnar struts 74. For some applications, exactly one, exactly two,exactly three (as shown and described above), exactly four, or five ormore of circumferential stent meanders 76 are thus shaped.

For some applications, outward protrusions 70 are cascaded around stent420.

Reference is now made to FIGS. 7A-B, which are schematic illustrationsof a barbed configuration of anchoring system 10, in accordance with anapplication of the present invention. In this configuration, anchoringsystem 10 comprises a radially-expandable stent 520, which is oneconfiguration of stent 20 described hereinabove with reference to FIGS.1 and 2A-D. As mentioned above, anchoring system 10 typically comprisesone or more tissue anchors 30 and one or more tethers 34 that connectthe stent to the one or more tissue anchors. Also as mentioned above,stent 20, when unconstrained in the radially-expanded state, is shapedso as to define one or more tether interfaces 50 at one or more tethercircumferential locations 52, respectively.

In this configuration, unlike the configurations shown in the otherfigures, outward protrusions 70 are shaped so as to define respectivebarbs 530, when stent 520 is unconstrained in the radially-expandedstate (i.e., no forces are applied to the stent by a delivery tool, wallof a body vessel, or otherwise). The barbs may aid in securinghigher-securement portion 64 of stent 520 to the vessel wall. The barbsmay protrude from one or more of columnar struts 74 of higher-securementportion 64, as shown, or from one or more of circumferential stentmeanders 76 of higher-securement portion 64 (configuration not shown).

Medical Applications

The anchoring system and stents described herein may be used for anumber of different medical applications, including but not limited tothe following applications. For some of these applications, tissueanchors 30 and tethers 34 are not provided.

-   -   The anchor system and stents described herein may be used in        tricuspid valve repair, such as described hereinabove with        reference to FIGS. 5A-D. One of the stents may be used as an        anchor point in the vena cava, to tether the tissue anchor which        is coupled to the native valve (typically at the        anterior-posterior commissure), thus lowering the        anterior-posterior commissure and diminishing regurgitation.    -   The stents described herein may be used in aortic transcatheter        valve implantation (TAVI), as a frame for the valve. The unique        designs of the stent allow anchoring the prosthetic valve more        securely to the native annulus, thereby preventing the        prosthetic valve from migration at early and midterm follow-up.        The stents described herein may also be used for mitral,        pulmonary, and tricuspid replacement, using a transfemoral,        transaxillary, transaortic, or transapical approach.    -   The stents described herein may be coupled to a filter, and may        be used, for example, as a vena cava filter in patients        suffering from a disorder of coagulation, in order to prevent        pulmonary thromboembolism.    -   The stents described herein may be used as a transjugular        intrahepatic portocaval shunt (TIPS) in patients suffering from        cirrhosis and portal hypertension.    -   The stents described herein may be used for endoprosthesis        placement in aortic abdominal and bisiliac vascular aneurism.    -   The stents described herein may be used for thoracic        endovascular aortic repair (TEVAR) or for traditional open        surgery elephant trunk or frozen elephant trunk technique in        descending aortic thoracic and in Stanford Type A aortic        dissection.    -   The stents described herein may be used for treating prostatic        hypertrophy in patients suffering from prostate enlargement.    -   The stents described herein may be used be used to stent        oncologic patients suffering from partial obstruction of the        trachea.

As used in the present application, including in the claims, “tubular”means having the form of an elongated hollow object that defines aconduit therethrough. A “tubular” structure may have variedcross-sections therealong, and the cross-sections are not necessarilycircular. For example, one or more of the cross-sections may begenerally circular, or generally elliptical but not circular, orcircular.

The scope of the present invention includes embodiments described in thefollowing applications, which are assigned to the assignee of thepresent application and are incorporated herein by reference. In anembodiment, techniques and apparatus described in one or more of thefollowing applications are combined with techniques and apparatusdescribed herein:

-   U.S. application Ser. No. 12/692,061, filed Jan. 22, 2010, which    published as US Patent Application Publication 2011/0184510;-   International Application PCT/IL2011/000064, filed Jan. 20, 2011,    which published as PCT Publication WO 2011/089601, and U.S.    application Ser. No. 13/574,088 in the national stage thereof, which    published as US Patent Application Publication 2013/0046380;-   U.S. application Ser. No. 13/188,175, filed Jul. 21, 2011, which    published as US Patent Application Publication 2012/0035712;-   U.S. application Ser. No. 13/485,145, filed May 31, 2012, which    published as US Patent Application Publication 2013/0325115;-   U.S. application Ser. No. 13/553,081, filed Jul. 19, 2012, which    published as US Patent Application Publication 2013/0018459;-   International Application PCT/IL2012/000282, filed Jul. 19, 2012,    which published as PCT Publication WO 2013/011502;-   U.S. Provisional Application 61/750,427, filed Jan. 9, 2013,    entitled, “Soft tissue anchors and implantation techniques”; and-   International Application PCT/IL2014/050027, filed Jan. 9, 2014,    which published as PCT Publication WO 2014/108903.

In particular, the stents described herein may be used as one or more ofthe stents described in the above-listed applications, in combinationwith the other techniques described therein.

It will be appreciated by persons skilled in the art that the presentinvention is not limited to what has been particularly shown anddescribed hereinabove. Rather, the scope of the present inventionincludes both combinations and subcombinations of the various featuresdescribed hereinabove, as well as variations and modifications thereofthat are not in the prior art, which would occur to persons skilled inthe art upon reading the foregoing description.

1-32. (canceled)
 33. Apparatus for use with a plurality of tissueanchors and a plurality of tethers, the apparatus comprising: aradially-expandable stent, which, when unconstrained in aradially-expanded state, is generally tubular and shaped so as todefine: a plurality of tether interfaces at a plurality of tethercircumferential locations, respectively, each of which tether interfacesextends circumferentially contiguously around a portion of acircumference of the stent, a plurality of lower-securement portionsthat extend (a) along at least respective contiguous lower-securementaxial segments of the stent and (b) circumferentially around respectivecontiguous lower-securement circumferential portions of the stent,wherein (i) each of the lower-securement axial segments includes one ormore of the tether interfaces, (ii) each of the lower-securementcircumferential portions includes one or more of the tether interfaces,and (iii) the lower-securement circumferential portions have respectivecircumferential arcs, a plurality of higher-securement portions thatextend (a) along at least respective contiguous higher-securement axialsegments of the stent and (b) circumferentially around respectivehigher-securement circumferential portions of the stent, collectively atall circumferential locations other than those of the lower-securementcircumferential portions, wherein the lower- and the higher-securementportions alternate around the stent, and a plurality of outwardprotrusions at respective circumferential locations around thehigher-securement portions, and not around the lower-securementportions, such that each of the higher-securement portions includes oneor more of the outward protrusions.
 34. The apparatus according to claim33, wherein the circumferential arcs of the lower-securementcircumferential portions are equal to one another.
 35. The apparatusaccording to claim 33, wherein the higher-securement circumferentialportions have respective circumferential arcs that are equal to oneanother.
 36. The apparatus according to claim 33, wherein thecircumferential arcs of the lower-securement circumferential portionsare equal to one another, and wherein the higher-securementcircumferential portions have respective circumferential arcs that areequal to one another.
 37. The apparatus according to claim 65, whereinthe stent is shaped so as to define a plurality of tension-distributingelements, which (a) extend along at least respectivetension-distribution axial segments of the stent at the tethercircumferential locations, respectively, (b) define the tetherinterfaces, respectively, and (c) are configured to distribute tensionapplied by the tethers, respectively, along the tension-distributionaxial segments of the stent, respectively.
 38. The apparatus accordingto claim 37, wherein the tension-distribution axial segments axiallycoincide with the lower-securement axial segments, respectively.
 39. Theapparatus according to claim 37, wherein the tension-distributingelements and the stent are fabricated from a single unit.
 40. Theapparatus according to claim 37, wherein each of thetension-distributing elements has a circumferential arc of between 1 and15 degrees, when the stent is unconstrained in the radially-expandedstate.
 41. The apparatus according to claim 37, wherein an axial lengthof each of the tension-distributing elements equals at least 15% of anaxial length of the stent.
 42. (canceled)
 43. The apparatus according toclaim 33, wherein the lower-securement axial segment of the stentextends along at least 30% of an axial length of the stent, when thestent is unconstrained in the radially-expanded state.
 44. (canceled)45. The apparatus according to claim 33, wherein an interior of thestent defines a right circular cylindrical shape having a radius, andwherein the outward protrusions extend radially outward from thecylindrical shape by a distance equal to between 5% and 25% of theradius, when the stent is unconstrained in the radially-expanded state.46. The apparatus according to claim 65, wherein the tether interfacesare shaped so as to define respective one or more openings through whichthe tethers are respectively coupled. 47-50. (canceled)
 51. Theapparatus according to claim 33, wherein the stent, when unconstrainedin the radially-expanded state, is shaped so as to define a same numberof the tether interfaces and the lower-securement portions.
 52. Theapparatus according to claim 51, wherein the tether circumferentiallocations are circumferentially centered in the lower-securementportions, respectively.
 53. The apparatus according to claim 33, whereinthe outward protrusions are rotationally-asymmetrically distributedaround the circumference of the stent, when the stent is unconstrainedin the radially-expanded state.
 54. The apparatus according to claim 33,wherein the outward protrusions are periodically distributed around eachof the higher-securement circumferential portions, when the stent isunconstrained in the radially-expanded state. 55-56. (canceled)
 57. Theapparatus according to claim 33, wherein each of the circumferentialarcs of the lower-securement circumferential portions equals at least200% of an average of circumferential distances between circumferentialmidpoints of circumferentially-adjacent ones of the outward protrusionsaround the higher-securement portions, when the stent is unconstrainedin the radially-expanded state.
 58. The apparatus according to claim 33,wherein the stent comprises a plurality of columnar struts and aplurality of circumferential stent meanders coupled to the columnarstruts at respective axial locations, and wherein one or more of thecircumferential stent meanders are shaped so as to define the outwardprotrusions at the respective circumferential locations around thehigher-securement portions, when the stent is unconstrained in theradially-expanded state.
 59. The apparatus according to claim 58,wherein, when the stent is unconstrained in the radially-expanded state,at least one of the circumferential stent meanders is shaped so as todefine (a) around the higher-securement portions, the outwardprotrusions, and (b) around the lower-securement portions, respectivearcs of a circle if the circumferential stent meander is projected ontoa plane perpendicular to a longitudinal axis of the stent. 60-62.(canceled)
 63. The apparatus according to claim 33, wherein each of thetether interfaces extends circumferentially contiguously around lessthan 30 degrees of the circumference of the stent.
 64. The apparatusaccording to claim 33, wherein the apparatus further comprises theplurality of tissue anchors.
 65. The apparatus according to claim 33,wherein the apparatus further comprises the plurality of tethers, whichhave respective first longitudinal portions that are coupled to theplurality of tether interfaces, respectively.
 66. The apparatusaccording to claim 65, wherein the apparatus further comprises theplurality of tissue anchors, and wherein the plurality of tethers haverespective second longitudinal portions, different from the respectivefirst longitudinal portions, that are coupled the plurality of tissueanchors, respectively.
 67. The apparatus according to claim 33, whereineach of the respective circumferential arcs of the lower-securementcircumferential portions is between 30 and 90 degrees.